Growing tomatoes solo in a row works, but you’re missing out. Strategic companion planting makes tomatoes stronger, more pest-resistant, and more productive — all without chemicals or extra effort.

Some plants actively help tomatoes by repelling pests, improving soil, or attracting beneficial insects. Others compete with tomatoes for nutrients and should be kept far away. Knowing the difference changes everything.

Here’s exactly what to plant with tomatoes and why.

How Companion Planting Works With Tomatoes

Tomatoes are vulnerable to a few major pests: hornworms, aphids, spider mites, and whiteflies. They also benefit from enriched soil and improved pollination. Companion plants address these needs in three ways:

Pest repelling: Some plants emit strong scents that confuse or deter tomato pests. Marigolds repel hornworms. Basil repels spider mites and whiteflies.

Pest trapping: Some plants attract pests away from tomatoes or trap them. Nasturtiums attract aphids — they become a sacrificial crop so aphids leave tomatoes alone.

Soil enrichment: Nitrogen-fixing plants (legumes) add nitrogen to soil, reducing the need for fertilizer and boosting tomato growth.

The Best Companion Plants for Tomatoes

Basil

Why it works: Basil is the classic tomato companion for good reason. It repels spider mites, whiteflies, and aphids — three of the most common tomato pests. It’s also delicious, so you benefit twice.

How to plant: Basil and tomatoes grow side by side beautifully. Space basil about 6 inches from the tomato stem. Both love sun and warm soil, so they thrive in the same conditions.

Bonus: Harvest basil regularly to encourage bushier growth. Use it fresh in sauces with your homegrown tomatoes.

Carrots

Why it works: Carrots have a deep root system that doesn’t compete with tomato roots (which are shallower). They improve soil structure and their thin leaves don’t shade tomatoes.

How to plant: Sow carrot seeds directly around the tomato base, about 3 inches away. Carrots take 60–80 days to mature, so you’ll harvest them well before tomato season peaks.

Real benefit: You get a bonus crop without taking up additional space.

Marigolds

Why it works: Marigolds emit a strong scent that repels tomato hornworms — one of the most destructive tomato pests. They also attract beneficial insects and brighten the garden.

How to plant: Plant one or two marigolds near each tomato plant. They’re easy from seed or transplants. Space them about 12 inches from the tomato stem so they don’t crowd the plant as it grows.

Catch: The marigold needs to be flowering to be effective — plant them early so they’re established by the time hornworms appear (mid-June in most zones).

Borage

Why it works: Borage attracts pollinators and beneficial insects while repelling tomato hornworms and cabbage moths. It’s also edible — blue flowers are great in salads.

How to plant: Borage gets bushy and tall (2–3 feet). Plant it behind or to the side of tomatoes so it doesn’t shade them. Give it about 18 inches of space.

Note: Borage self-seeds readily. You’ll have it coming back next year once you plant it once.

Parsley and Cilantro

Why it works: Both herbs attract beneficial insects, particularly parasitic wasps that prey on tomato hornworms and other pests. They also don’t compete with tomatoes for nutrients or space.

How to plant: Interplant parsley and cilantro around tomatoes. Both are fast-growing (30–50 days) and occupy minimal space. You can harvest leaves continuously and replant.

Nasturtiums (The Sacrifice Play)

Why it works: Nasturtiums are a “trap crop.” Aphids prefer them over tomatoes, so nasturtiums attract aphids away from your tomato plants. You essentially give up the nasturtiums to save the tomatoes.

How to plant: Plant nasturtiums 12–18 inches from tomatoes (far enough that they won’t directly compete). Don’t worry if they get infested with aphids — that’s the plan. The aphids stay busy on the nasturtiums instead of moving to tomatoes.

Worth it: This strategy reduces tomato pest pressure significantly. One or two nasturtium plants per tomato plant is usually enough.

Chives

Why it works: Chives repel spider mites and other soft-bodied pests. They’re perennial, so once planted, they come back year after year with minimal effort.

How to plant: Plant chives near the tomato base — they stay low and won’t shade the plant. Space about 8 inches away. Chives can handle partial shade, so they’ll grow even if tomato foliage creates light shade.

What NOT to Plant With Tomatoes

Brassicas (Cabbage, Broccoli, Cauliflower)

These heavy feeders compete with tomatoes for nitrogen and nutrients. If you’re growing both, plant them far apart (at least 3 feet) or in different garden sections.

Fennel

Fennel allelopathy — it releases chemicals that inhibit the growth of nearby plants, including tomatoes. Keep fennel completely separate from tomato beds.

Corn

Corn and tomatoes compete for similar nutrients and both attract hornworms. Keep them at least 5 feet apart.

Potatoes

Potatoes and tomatoes are both susceptible to early blight and late blight (fungal diseases). Planting them near each other spreads disease risk. Space them far apart or skip potatoes if you’re growing tomatoes.

Dill

While dill attracts beneficial insects (good), it also attracts hornworms (bad). The drawbacks outweigh the benefits — better options exist.

The Ideal Tomato Bed Layout

Picture your tomato plant in the center. Here’s the optimal ring:

  • Directly adjacent (6 inches): Basil, chives, parsley
  • 12 inches out: Marigolds, small nasturtium transplants
  • 18 inches out (behind): Borage (if space allows)
  • Interspersed: Carrot seeds sown directly

This setup repels the major pests, attracts beneficials, enriches soil, and gives you bonus harvests of herbs and vegetables.

Container and Small Space Version

If you’re growing tomatoes in containers or have limited space:

  • Plant one tomato per pot (5+ gallons)
  • Add one basil plant to the same pot
  • Plant marigolds in adjacent smaller containers
  • Use nasturtiums in a hanging basket nearby

The principles stay the same — you’re just condensing the layout.

When to Plant Companions

Most companion plants should be in place before or at the same time as tomatoes. If you’re planting tomato transplants in May, get basil, marigolds, and other companions in the ground by early May as well.

For carrot seeds and direct-seeded herbs, plant them once soil has warmed and tomatoes are established (by mid-May in most zones).

The Real Payoff

Companion planting isn’t magic, but it works. Gardens with strong companion planting strategies get:

  • 20–30% fewer pest problems
  • Better soil fertility
  • Healthier, more productive plants
  • Bonus harvests of herbs and vegetables

You’re not replacing pest management entirely — monitor plants and handpick hornworms regardless. But companion planting significantly reduces problems before they start.

The best part? You’re growing food or useful plants anyway. Basil and carrots have real value. You’re not planting sacrificial crops just for show — you’re optimizing every square inch.

Plant your tomatoes. Surround them strategically. Harvest both tomatoes and healthier companion crops all season.